speaking of the clippard solenoids, I bought a couple and the 1st one didnt fully close for some reason, It would leak a bubble every couple seconds out. I swapped it for a different one(same model)...

Throw that "rule" out the window, especially for T5HO with good reflectors. But to consider a "rule" then 2wpg of T5HO will grow pretty much anything from what I have seen with good CO2 on 4' tanks....